Euconnus taiwanus, Franz, 1985

Jałoszyński, Paweł, 2022, Taxonomy of ' Euconnus complex'. Part XXIV. Intermediate forms between Psomophus, Eupentarius and Euconnus s. str. in the East Palaearctic fauna unify problematic subgenera (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 5194 (3), pp. 343-391 : 363

5. Euconnus taiwanus species group

Two previously described Far Eastern species, E. taiwanus Franz, 1985a , and E. fukiensis Franz, 1985a , show problematic characters that so far made it impossible to decide to which subgenus of Euconnus they should be assigned. Many similar species were placed in Euconophron (currently junior synonym of Eupentarius Reitter ), mainly based on the shape of the pronotum, which is round and broadest slightly behind middle. However, the pronotum does not have the median antebasal pit, typical of the type species of Eupentarius (and Euconophron , and all previously recognized subgenera that have been merged with Eupentarius ). The clearly trimerous antennal club, but with the antennomere 9 distinctly smaller than 10, did not allow for placing these species in the former subgenus Napochus , which has a somewhat similar pronotum (although in its type species broadest at base). Examination of numerous specimens from Japan, primarily from the Ryūkyū, revealed that this group includes at least six externally very similar species, but showing an enormous diversity in the aedeagal structures. They are all treated here as members of the Euconnus taiwanus species group, which is characterized by the above-mentioned two features: the antennae remarkably short and compact, with trimerous clubs, but antennomere 9 always much narrower than 10; and the pronotum rounded at sides, broadest slightly behind middle or at middle, and with two pairs of antebasal pits. In addition, all members have distinctly elongate head, with strongly elevated supraantennal tubercles narrowly separated at middle and vertex slightly bulging posterodorsad; the pronotal base with two pairs of pits, of which inner pair is slightly larger than outer pair, lacking transverse groove or connected by faint, barely discernible groove; and thick bristles distributed on tempora, vertex and sides of pronotum. Aedeagi are so diverse that it is not possible to include any genital characters into the diagnosis of this group.

Morphological structures of this group were studied in detail to make sure that these unusual species indeed belong in Euconnus . The following diagnostic features of Euconnus were found in E. taiwanus : the head ( Fig. 64 ) with anteriorly situated eyes, with occipital constriction; the basisternal region of prosternum ( Fig. 65 ) much shorter than the coxal region (= furcasternum); the procoxal cavities closed by postcoxal lobes of furcasternum and hypomera; the notosternal sutures and hypomeral ridges present; mesocoxal rests on the metaventrite ( Fig. 67 ) separated by a keel-like, carinate mesoventral intercoxal process; and metacoxae separated by the metaventral intercoxal process. Males in this group are winged and have fully developed metanota ( Fig. 66 ), with alacristae almost as long as length of mesoscutum + mesoscutellum. The mesoscutellar shield ( Fig. 66 ) is not exposed between elytra in intact specimens.

The following species are included in the E. taiwanus group: E. taiwanus (Taiwan) , E. fukiensis ( China: Fujian), and four newly described Japanese species: E. bibaculatus , E. cryptoiriomotensis , E. oitaensis , and E. banana . As the two first species were inadequately described, they are redescribed in the present paper.

Figures

FIGURES 64‒67. Euconnus taiwanus Franz, male. Head in dorsal view (64); prothorax in ventral view (65); meso- and metanotum in dorsal view (66); pterothorax in ventral view (67). Abbreviations: alc, alacrista; bst, basisternal region of prosternum; fov, fovea; fr, frons; hyr, hypomeral ridge; lfa, lateral furcal arm; msvp, mesoventral process; mtvp, metaventral process; nr, neck region; nss, notosternal suture; occ, occipital constriction; pcc, procoxal cavity; pn3, metapostnotum; sc3+scl3, metascutum and metascutellum; ss, scutellar shield; vt, vertex.